In many cases we are interested in events much rarer than those described
by a Gaussian approximation. It is then useful to consider fluctuations
of \(a\)  that are of order \(T\) , rather than \(\sqrt{T}\) . For these
large fluctuations, a generalization of the central limit theorem,
called a large deviation result [1]}, states that
\(\rho (a,T)\underset{T\rightarrow \infty }{\asymp }\mbox{e}^{-TI\left[a\right]},\) 
